Military tension surrounding the Korean Peninsula is escalating dangerously, with Washington and Pyongyang intensifying their war of words and the United States flying B-1B Lancer bombers off the North Korean coast.

North Korean Foreign Minister Ri Yong-ho has said missile attacks against the U.S. mainland would be inevitable as U.S. President Donald Trump has kept insulting the dignity of the Kim Jong-un regime.

In an address to the United Nations General Assembly, Sunday, Ri angrily responded to Trump's earlier speech Tuesday, in which he referred to Kim as "rocket man." At the time, Trump also threatened to "totally destroy" the North if the U.S. was forced to defend itself or its allies against a North Korean attack.

Ri said Trump's insult makes "our rocket's visit to the entire U.S. mainland all the more inevitable," calling him a "mentally deranged" person who used "reckless and violent words."

Ri also said his country will take "merciless preventive action" if Washington shows any signs of a "decapitating operation on our headquarters or a military attack against our country."

"None other than Trump himself is on a suicide mission," Ri said. "In the case innocent lives of the U.S. are harmed because of this suicide attack, Trump will be held totally responsible."

Pyongyang's top diplomat also downplayed the latest U.N. sanctions imposed on the North for its sixth nuclear test as "unjustifiable." On Sept. 11, the U.N. Security Council unanimously approved the new sanctions resolution, targeting oil supplies to the impoverished state for the first time.

Trump responded to Ri's speech on Twitter, saying, "Just heard Foreign Minister of North Korea speak at U.N. If he echoes thoughts of Little Rocket Man, they won't be around much longer!"

On Friday, the North's young leader released a statement to criticize Trump's U.N. speech. Calling the U.S. president "a rogue and a gangster fond of playing with fire, rather than a politician," Kim said "we will consider with seriousness exercising of a corresponding, highest level of hard-line countermeasure in history" in response to Trump's threat to destroy the North.

Referring to Kim's statement, Ri told reporters in New York that the repressive state could conduct the most powerful detonation of a hydrogen bomb in the Pacific.

On Sunday, the North's state-run Korean Central News Agency (KCNA) reported more than 100,000 North Korean people held a massive anti-U.S. demonstration in Pyongyang over the weekend.

Show-of-force by US

Hours before Ri delivered his speech, the U.S. armed forces flew B-1B Lancer bombers further north of the Demilitarized Zone (DMZ) than any other American warplanes in the 21st century, adding fuel to the ongoing war of words between Washington and Pyongyang.

The Pentagon announced that U.S. Air Force (USAF) B-1B bombers from Guam, along with USAF F-15C Eagle fighter escorts from Okinawa in Japan, flew in international airspace over waters east of North Korea.

"This is the farthest north of the DMZ any U.S. fighter or bomber aircraft have flown off North Korea's coast in the 21st century, underscoring the seriousness with which we take the DPRK's reckless behavior," Pentagon spokeswoman Dana W. White said.

DPRK stands for the Democratic People's Republic of Korea, the North's official name.

"This mission is a demonstration of U.S. resolve and a clear message that the president has many military options to defeat any threat. North Korea's weapons program is a grave threat to the Asia-Pacific region and the entire international community," she said. "We are prepared to use the full range of military capabilities to defend the U.S. homeland and our allies."

The B-1B is a four-engine supersonic, variable-sweep wing, strategic bomber with a speed of Mach 2. The aircraft is capable of carrying the largest payload of both guided and unguided weapons in the USAF inventory.

The aircraft was designed as a nuclear bomber but is no longer armed with nuclear weapons in accordance with a bilateral treaty between the United States and Russia on the reduction and limitation of strategic offensive arms. But the Lancer is capable of carrying the AGM-86B air launch cruise missile (ALCM) and the AGM-69 short-range attack missile, which are capable of striking the North's key nuclear facilities as well as its military leadership.